Air traffic control officers (ATCOs) are rigorously selected from the vast number of applicants and extensively trained, in order to have the required psychological and behavioural characteristics for this stressful occupation, as well as specialised performance competencies while controlling air traffic, such as situational awareness, workload management, problem-solving and decision-making. Recent studies have demonstrated the possible improvements of ATCO selection and training processes by using physiological, speech and oculometric features related to stress resilience, cognitive load, visual attention and fatigue. The functional near-infrared spectroscopy (fNIRS) is a brain imaging technique which provides a good insight into brain activation by measuring the haemoglobin concentration in the prefrontal cortex, which is one of the key brain areas responsible for complex cognitive behaviour, decision-making, working memory, and stress regulation. This paper focuses on the ATC performance competencies that could be measured with the fNIRS, demonstrates computational processing of signals obtained with this technique, and discusses the applicability of fNIRS measurements in the current ATC selection and training procedures. The experimental paradigm and the results obtained from the paradigm demonstrate that fNIRS shows differences in brain activation among individuals during cognitive tasks, thus allowing the more objective performance measurement.